Method and apparatus for performing TCP communication in a wireless communication system

ABSTRACT

A method and an apparatus for performing Transmission Control Protocol (TCP) communication at a network node in a wireless communication system are provided. The method includes receiving, by the network node that connects between a Mobile Station (MS) and a data network, a TCP KeepAlive packet for maintaining a TCP connection established between a correspondent node and the MS through the data network from the correspondent node, transmitting, by the network node, when it is determined that the MS is in an idle mode upon receiving the TCP KeepAlive packet, an acknowledgement packet in response to the TCP KeepAlive packet to the correspondent node, and transmitting, by the network node, indication information indicating the reception of the TCP KeepAlive packet to the MS.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed on Feb. 13, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0015421, the entiredisclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system. Moreparticularly, the present disclosure relates to a method and apparatusfor performing data communication by Transmission Control Protocol (TCP)in a wireless communication system.

BACKGROUND

Research has been conducted to provide various services at or above 100Mbps to users and the services are under deployment as a 4^(th)Generation (4G) communication system. Particularly, support ofhigh-speed services with mobility and Quality of Service (QoS) ensuredis an active study area in a Broadband Wireless Access (BWA)communication system such as Wireless Local Area Network (WLAN) andWireless Metropolitan Area Network (WMAN) systems.

Transmission Control Protocol (TCP)/Internet Protocol (IP) is widelyused for reliable connectivity between two end users irrespective of thetype of communication system. TCP/IP means that an IP layer and itsoverlying TCP layer are used. Besides the TCP layer, many other layersmay exist above the IP layer. For example, packets generated in variousprotocols such as User Datagram Protocol (UDP), Internet Control MessageProtocol (ICMP), Internet Group Management Protocol (IGMP), andReal-Time Protocol (RTP) are encapsulated by the IP protocol, prior totransmission.

If no process at either endpoint of a TCP connection transmits data toits peer node, nothing is exchanged between both TCP modules. Unlessthis TCP connection is controlled, the TCP connection may be left as itis for hours, days, or months. Therefore, even though a relay router hasfailed or re-reruns or a link is damaged and then recovered, the TCPconnection is maintained as long as at least one of the hosts (i.e., endusers) at both endpoints of the TCP connection does not re-run. This TCPconnection serves as a kind of garbage, consuming system resources. Inthis context, TCP KeepAlive is used to prevent resource waste caused byunnecessary maintenance of a TCP connection.

In TCP KeepAlive, a TCP KeepAlive probe packet is transmitted to a TCPpeer node in a predetermined cycle. If a TCP ACKnowledgment (ACK) is notreceived in response to the TCP KeepAlive probe packet, a TCP connectionsession is closed, that is, released. In general, a timer for TCPKeepAlive may be set to any time from 15 minutes to 2 hours.

If one of TCP end users is a Mobile Station (MS) that accesses an IPnetwork through a wireless communication system, the MS may access theIP network through a Base Station (BS) and an Access Service NetworkGateWay (ASN-GW). In the absence of traffic transmitted/received via aradio interface for a predetermined time, the MS may switch to an idlemode and turns off a wireless module, thereby minimizing powerconsumption. A timer for idle mode is generally set to a smaller valuethan the timer for TCP KeepAlive.

If the timer for TCP KeepAlive expires after the MS enters the idlemode, a remote end user generates a KeepAlive packet and transmits theKeepAlive packet to an ASN-GW being a core entity of a Core Network (CN)to which the MS is connected through the IP network, without knowledgeof the state of the MS. A BS of a radio access network pages the MS inresponse to a notification of the ASN-GW so that the KeepAlive packetmay be transmitted to the MS. The MS performs network reentry to the BSin response to the paging, receives the KeepAlive packet, and repliesthe remote end user with an ACK packet. Subsequently, when apredetermined time elapses without packet transmission, the MS returnsto the idle mode.

The network reentry involves many procedures for MS re-authentication,Layer 1 (L1)/Layer 2 (L2) resource reallocation, and reconfiguration ofa radio connection. Accordingly, network reentry and paging performedjust for TCP KeepAlive result in unnecessary resource consumption ofrelated entities and radio interfaces.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and apparatus for performingTransmission Control Protocol (TCP) KeepAlive in a wirelesscommunication system.

Another aspect of the present disclosure is to provide a method andapparatus for preventing a Mobile Station (MS) from performingunnecessary paging and network reentry for TCP KeepAlive in a wirelesscommunication system.

Another aspect of the present disclosure is to provide a method andapparatus for performing TCP KeepAlive on behalf of an MS by a node of acore network in a wireless communication system.

In accordance with an aspect of the present disclosure, a method forperforming TCP communication at a network node in a wirelesscommunication system is provided. The method includes receiving, by thenetwork node that controls a connection between an MS and a datanetwork, a TCP KeepAlive packet for maintaining a TCP connectionestablished between a correspondent node and the MS through the datanetwork from the correspondent node, determining whether the MS is in anidle mode in response to the reception of the TCP KeepAlive packet bythe network node, if the MS is in the idle mode, transmitting anacknowledgement packet in response to the TCP KeepAlive packet to thecorrespondent node by the network node, and transmitting indicationinformation indicating the reception of the TCP KeepAlive packet to theMS by the network node.

In accordance with another aspect of the present disclosure, a methodfor performing TCP communication at a network node in a wirelesscommunication system is provided. The method includes receiving, by thenetwork node that controls a connection between an MS and a datanetwork, a location update request message including indicationinformation for TCP KeepAlive from the MS in an idle mode, transmittinga TCP KeepAlive packet to a correspondent node that establishes a TCPconnection with the MS through the data network in response to theindication information by the network node, receiving a response to theTCP KeepAlive packet from the correspondent node by the network node,and transmitting a location update response message including responseinformation indicating a result of the transmission of the TCP KeepAlivepacket to the MS by the network node.

In accordance with another aspect of the present disclosure, a methodfor performing Transmission Control Protocol (TCP) communication at aMobile Station (MS) in a wireless communication system is provided. Themethod includes, if a timer for TCP KeepAlive for a TCP connectionestablished between the MS in an idle mode and a correspondent nodethrough a data network expires, transmitting a location update requestmessage including indication information for TCP KeepAlive to a networknode that controls a connection between the MS and the data network,receiving a location update response message including responseinformation indicating a TCP KeepAlive result from the network node,and, if the response information indicates successful reception of anacknowledgement packet for TCP KeepAlive from the correspondent node atthe network node, resetting the timer for TCP KeepAlive.

In accordance with another aspect of the present disclosure, a networknode for controlling a connection between an MS and a data network in awireless communication system is provided. The network node includes anetwork interface configured to receive a TCP KeepAlive packet formaintaining a TCP connection established between a correspondent nodeand the MS through the data network from the correspondent node and totransmit an acknowledgement packet in response to the TCP KeepAlivepacket to the correspondence node, and a controller configured todetermine whether the MS is in an idle mode in response to the receptionof the TCP KeepAlive packet, to control, if the MS is in the idle mode,the network interface to transmit an acknowledgment packet in responseto the TCP KeepAlive packet to the correspondent node, and to controlthe network interface to transmit indication information indicating thereception of the TCP KeepAlive packet to the MS.

In accordance with another aspect of the present disclosure, a networknode for controlling a connection between an MS and a data network in awireless communication system is provided. The network node includes anetwork interface configured to receive a location update requestmessage including indication information for TCP KeepAlive from the MSin an idle mode, to transmit a TCP KeepAlive packet to a correspondentnode that establishes a TCP connection with the MS through the datanetwork in response to the indication information, and to receive aresponse to the TCP KeepAlive packet from the correspondent node, and acontroller configured to, upon receipt of a response to the TCPKeepAlive packet, control the network interface to transmit a locationupdate response message including response information indicating aresult of the transmission of the TCP KeepAlive packet to the MS.

In accordance with another aspect of the present disclosure, an MS forperforming TCP communication in a wireless communication system isprovided. The MS includes a controller configured to, if a timer for TCPKeepAlive for a TCP connection established between the MS in an idlemode and a correspondent node through a data network expires, generateindication information for TCP KeepAlive, and a radio interfaceconfigured to transmit a location update request message including theindication information to a network node that controls a connectionbetween the MS and the data network and to receive a location updateresponse message including response information indicating a TCPKeepAlive result from the network node. If the response informationindicates successful reception of an acknowledgement packet for TCPKeepAlive from the correspondent node at the network node, thecontroller resets the timer for TCP KeepAlive.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a simplified configuration of a wirelesscommunication system to which the present disclosure is appliedaccording to the related art;

FIG. 2 illustrates an Internet Protocol (IP) packet format according toan embodiment of the present disclosure;

FIG. 3A illustrates a User Datagram Protocol/Internet Protocol (UDP/IP)packet format according to an embodiment of the present disclosure;

FIG. 3B illustrates a Transmission Control Protocol/Internet Protocol(TCP/IP) packet format according to an embodiment of the presentdisclosure;

FIG. 4 illustrates a simplified procedure for opening a TCP sessionbetween end users by TCP 3-way handshake according to an embodiment ofthe present disclosure;

FIG. 5 illustrates a simplified procedure for closing a TCP sessionbetween end users by TCP 4-way handshake according to an embodiment ofthe present disclosure;

FIG. 6 is a diagram illustrating a signal flow for a KeepAlive procedurefor an idle-mode Mobile Station (MS) according to an embodiment of thepresent disclosure;

FIG. 7 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to an embodiment of the present disclosure;

FIG. 8 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to another embodiment of the presentdisclosure;

FIG. 9 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to another embodiment of the presentdisclosure;

FIG. 10 is a block diagram of a network node according to an embodimentof the present disclosure; and

FIG. 11 is a block diagram of an MS according to an embodiment of thepresent disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

The following description will be given of embodiments of the presentdisclosure intended to support Transmission Control Protocol (TCP)KeepAlive for a Mobile Station (MS) that accesses an Internet Protocol(IP) network through a radio access network and uses TCP/IP.

FIG. 1 illustrates a simplified configuration of a wirelesscommunication system to which the present disclosure is appliedaccording to the related art.

Referring to FIG. 1, an MS 102 accesses a BS 104 of a radio accessnetwork via a radio interface. The radio interface may conform to, forexample, World Interoperability for Microwave Access (WiMAX), 3rdGeneration Partnership Project (3GPP), Long Term Evolution (LTE), or thelike. The BS 104 connects the MS 102 to an IP network 110 being a publicdata network through a core entity of a core network, for example, anAccess Service Network GateWay (ASN-GW) 108 of the core network. APaging Controller (PC) 106 manages a state of the MS 102 and, whenneeded, pages the MS 102, in conjunction with a location server (notshown) of an operator network.

The ASN-GW 108 may be connected to the IP network 110 directly orthrough another core entity such as a Packet GateWay (P-GW) (not shown).The ASN-GW 108 is a first entity to receive an IP packet directed to theMS 102 in the core network.

The MS 102 may conduct IP communication with a Correspondence Node (CN)120 over the IP network 110, and various protocols may exist above an IPlayer. The type of a protocol existing at the IP layer is indicated byan IP header included in an IP packet.

FIG. 2 illustrates an IP packet format according to an embodiment of thepresent disclosure.

Referring to FIG. 2, an IP packet 200 includes Destination Address (DA)202 indicating a Medium Access Control (MAC) address of a receiver,Source Address (SA) 204 indicating a MAC address of a sender, EType 206indicating an IP version (IP version 4 (IPv4) or IP version 6 (IPv6)),IP Header 208, IP Datagram 210, and Cyclic Redundancy Checked (CRC) 212.

The IP Header 208 includes Version (VER) indicating a version number(IPv4 or IPv6) of the IP Header 208, Internet Header Length (IHL)indicating the size of the IP Header 208, Type of Service (ToS)indicating service quality of the transmitted IP packet 200, TotalLength indicating the total length of the IP Header 208 and the IPDatagram 210 in octets, Identification referred to by a higher layer,Don't Fragment (DF) and More Fragments (MF) which are flags indicatingpacket fragmentation-related control, Fragment Offset indicating afragmentation interval, Time To Live (TTL) indicating a valid time overwhich the IP packet 200 may stay in the network, Protocol ID 214, HeaderChecksum, Source IP Address (SA) indicating an IP address of the sender,Destination IP Address (DA) indicating an IP address of the receiver,and IP options supporting a variable length.

The 8-bit Protocol ID 214 indicates a layer that generates a packetabove the IP layer. If Protocol ID=1, this indicates Internet ControlMessage Protocol (ICMP), and if Protocol ID=2, this indicates InternetGroup Management Protocol (IGMP).

FIG. 3A illustrates a UDP/IP packet format according to an embodiment ofthe present disclosure.

Referring to FIG. 3A, a UDP/IP packet 300 includes UDP Header 302 andUDP Data 304 in the IP Datagram field 210 shown in FIG. 2. The UDPHeader 302 includes Source Port number (SP) 306 indicating a UDP sourceport number, Destination Port number (DP) 308 indicating a UDPdestination port number, UDP Length 310 indicating the total length ofthe UDP Header 302 and the UDP Data 304, and UDP Checksum 312.

If Protocol ID=6, this means that a TCP layer above the IP layergenerates the IP packet 200. In this case, a TCP packet is included inthe IP Datagram field 210.

FIG. 3B illustrates a TCP/IP packet format according to an embodiment ofthe present disclosure.

Referring to FIG. 3B, a TCP/IP packet 320 includes TCP Header 322 andTCP Data 324 in the IP Datagram field 210 shown in FIG. 2. The TCP Data324 may be omitted depending on the circumstances. The TCP Header 322includes SP 326 indicating a TCP source port number, DP 328 indicating aTCP destination port number, Sequence Number 330, Acknowledgment Number332, TCP Header Length (THL) 334, control flags 335 used to control TCPconnection and termination, Window Size 336, TCP Checksum 338, UrgentPointer 340, and TCP options 342.

A TCP session between end users is identified by the SP 326 and the DP328. That is, TCP sessions of an IP connection using the same IP addressare transmitted or received to or from a higher-layer applicationprogram by source/destination port numbers. The SP 326 identifies asource application program. At an initial connection attempt (SYN=1),the SP 326 is generated randomly. Unlike UDP, the source port number maynot be 0 in TCP. Accordingly, the SP 326 may range from 1 to 65535.

The DP 328 identifies a destination application program. At an initialconnection attempt (SYN=1), the DP 328 is generated randomly. The DP 328may also range from 1 to 65535.

The Sequence Number 330 specifies the sequence of transmitted data. TheSequence Number 330 is increased by 1 for each 1-byte data. If theSequence Number 330 exceeds 2³², the Sequence Number 330 may be reset.

The Acknowledgment Number 332 indicates the byte position of receiveddata, which is set to (the sequence number of the position of completelyreceived data+1). When an ACK flag is 1 (e.g., ON), the AcknowledgmentNumber field 332 is used.

The THL 334 indicates the starting position of the TCP Data 324. Sincethe TCP Data 324 follows the TCP Header 322, the THL 334 may beinterpreted as indicating the size of the TCP Header 322.

The TCP control flags 335 include Urgent (URG), ACK, Push (PSH), Reset(RST), Synchronization Number (SYN), and Finish (FIN). The URG is a flagindicating inclusion of urgent data, indicating that the followingUrgent Pointer 340 is valid. For example, when an interrupt command istransmitted, the URG may be used. The ACK is a flag indicating inclusionof a valid ACK number in the TCP header 322. In TCP 3-way handshake, theACK flags of all TCP packets except for an initial TCP packet are set to1 (e.g., ON). The PSH is a flag requesting immediate transfer ofreceived data to an application program. Thus the TCP layer immediatelytransmits the TCP packet to a higher-layer process in response to thePSH flag.

The RST is a flag set when the TCP connection is to be terminated orrejected. One TCP end user may force termination of an ongoing TCPconnection by transmitting a TCP packet with RST set to 1 (e.g., ON).The SYN is a flag used to synchronize the ACK number, when both endusers set the SYN to 1 (e.g., ON) in TCP 3-way handshake. The FIN is aflag set to close a TCP connection. If both end users transmit the FINflag, the TCP connection is closed.

The Window Size 336 indicates a maximum buffer size for a current state.The receiver may indicate a receivable data size to the transmitter bythe Window Size field 336. The Urgent Pointer 340 is valid only when theURG flag is 1. The Urgent Pointer 340 indicates the last byte positionof data to be handled urgently.

FIG. 4 illustrates a simplified procedure for opening a TCP sessionbetween end users by TCP 3-way handshake according to an embodiment ofthe present disclosure.

Referring to FIG. 4, a transmitter 402 being a transmitting hostrequests a receiver 404 to synchronize Sequence Number to 100 bytransmitting a sync packet with [SYN=1, ACK=0, Sequence Number=100] inoperation 412. In operation 414, the receiver 404 transmits an ACK/syncpacket with [SYN=1, Sequence Number=200, ACK=1, AcknowledgmentNumber=101] to the transmitter 402 in response to the sync packet. TheACK/sync packet indicates successful reception of the packet withSequence Number=100 transmitted by the transmitter 402 and requeststransmission of a packet with Sequence Number=101 and synchronization ofSequence Number to 200. Thus, TCP synchronization is acquired betweenthe transmitter 402 and the receiver 404. In operation 416, thetransmitter 402 transmits an ACK packet with [ACK=1, AcknowledgmentNumber=201] to the receiver 404. The ACK packet indicates successfulreception of the packet with Sequence Number=200 transmitted by thereceiver 404 (i.e., the packet transmitted in operation 414) and waitingfor a packet with Sequence Number=201.

FIG. 5 illustrates a simplified procedure for closing a TCP sessionbetween end users by TCP 4-way handshake according to an embodiment ofthe present disclosure.

Referring to FIG. 5, a transmitter 502 transmits a segment packet with[FIN=1, ACK=0, Sequence Number=J] to a receiver 504 to indicatetermination of a TCP connection in operation 512. In operation 514, thereceiver 504 transmits a segment packet with [ACK=1, AcknowledgmentNumber=J+1] to confirm the request of the transmitter 502. Herein, aconnection directed from the transmitter 502 to the receiver 504 isterminated but a reverse connection is still maintained. Therefore, thereceiver 504 may continue to transmit data to the transmitter 502.

In operation 516, the receiver 504 completes its transmission andtransmits a segment packet with [FIN=1, ACK=1, AcknowledgmentNumber=J+1, Sequence Number=K] to the transmitter 502 to indicaterelease of the TCP connection. The transmitter 502 completely terminatesthe TCP connection by transmitting an ACK packet with [ACK=1] inresponse to the request of the receiver 504 in operation 518.

If a TCP connection is maintained between both end users of the TCPconnection and no process of either end user transmits data to the otherend user, the TCP connection may be left as it is for hours, days, ormonths, thereby wasting resources. To prevent the resource waste, TCPKeepAlive is performed.

One of main purposes of TCP KeepAlive is to detect a dead peer. That is,when one of end users is dead, TCP KeepAlive is used to handle a one-wayopen connection state. Specifically, if a remote node is dead during TCPcommunication, a local node still opens a TCP connection and the deadremote node closes the TCP connection. Unless a network applicationprogram sets a timeout value or a TCP KeepAlive socket option, the abovestate is maintained, consuming resources until the local node isrebooted. TCP KeepAlive checks this state and closes an unnecessarysession of the TCP connection, thereby preventing unnecessary resourceconsumption.

In addition, TCP KeepAlive may be used to prevent disconnection causedby network inactivity. If a network node such as a Network AddressTranslation (NAT) proxy, a firewall, or a general server has notreceived a packet for a predetermined time, the network node may releasea related session. To prevent the session release, TCP KeepAlive is usedfor periodic packet transmission.

For TCP KeepAlive, a TCP KeepAlive probe packet is used. The TCPKeepAlive probe packet includes [ACK=1, Sequence Number=SDN.NXT−1] and adata field with no data or 1-byte garbage data. SND.NXT represents thenext sequence number for transmission. Since SND.NXT is equal to RCV.NXTindicating the next sequence number expected for reception, SND.NXT−1may be outside a window range.

An end user may transmit a TCP KeepAlive probe packet according to TCPconnection information set by an application program. A transmissioninterval and a transmission period of the TCP KeepAlive probe packet maybe changed according to TCP connection information set by theapplication program. If a related TCP session is valid, a TCP CN thathas received the TCP KeepAlive probe packet transmits a TCP ACK packetwith [ACK=1] and resets an internal timer used to determine when totransmit its TCP KeepAlive probe packet. On the contrary, if the relatedTCP session is not valid, the TCP CN transmits an RST packet [RST=1] sothat the end user transmitting the TCP KeepAlive probe packet mayterminate the TCP session.

FIG. 6 is a diagram illustrating a signal flow for a KeepAlive procedurefor an idle-mode MS according to an embodiment of the presentdisclosure.

Referring to FIG. 6, an MS exchanges packets with a CN via a TCPconnection through a BS, an ASN-GW, and an IP network (not shown). TheMS resets a timer 604 for idle mode after exchanging a last packet withthe CN via a radio interface in operation 612. When the timer 604 foridle mode expires, the MS performs a procedure for entering the idlemode with a paging controller in operation 614. If the MS successfullyenters the idle mode, the paging controller notifies the ASN-GW of thesuccessful switching of the MS to the idle mode and thus the ASN-GW isaware that the MS has entered the idle mode. Subsequently, upon receiptof a packet via a connection associated with the MS, the ASN-GW notifiesthe paging controller of the reception of the packet. The CN also startsa timer 602 for TCP KeepAlive after exchanging the last packet with theMS via the TCP connection in operation 612. The timer 602 for TCPKeepAlive is set to a value longer than the timer 604 for idle mode.Therefore, if the timer 602 for TCP KeepAlive expires after the MSswitches to the idle mode, the CN generates a TCP KeepAlive packet(i.e., a TCP KeepAlive probe packet) directed to the MS, withoutknowledge of the MS being placed in the idle mode in operation 616.

The TCP KeepAlive packet is transmitted to the ASN-GW through a P-GW(not shown) over the IP network. The ASN-GW is aware that the MS being adestination of the TCP KeepAlive packet is in the idle mode. Thus theASN-GW performs a paging procedure with the paging controller to wake upthe idle-mode MS in operation 618 and transmits a Paging Announcemessage for the MS to a BS (and neighbor BSs) in which the MS is finallylocated in operation 620. In operation 622, the BS (or the BSs)broadcasts a Mobile Paging Advertisement (MOB_PAG-ADV) message to pagethe MS. The MS performs network reentry to the BS in response to theMOB_PAG-ADV message in operation 624. The ASN-GW transmits the TCPKeepAlive packet to the MS through the BS, recognizing that the MS hasswitched from the idle mode by the network reentry.

In operation 626, the MS transmits an ACK packet to the CN in responseto the TCP KeepAlive packet in order to maintain the TCP connection.After transmitting the ACK packet, the MS resets the timer 604 for idlemode in operation 628. If the timer 604 for idle mode expires, the MSswitches to the idle mode. In addition, since a packet for a TCPconnection has been generated, the MS resets a timer for TCP KeepAlive.

To prevent unnecessary paging and network reentry procedures simply forTCP KeepAlive as described above, an entity of a core network, forexample, an ASN-GW responds to TCP KeepAlive on behalf of an MS andnotifies the MS of the behavior of the ASN-GW in an embodiment of thepresent disclosure.

FIG. 7 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to an embodiment of the present disclosure.In the illustrated case of FIG. 7, a network node is an entity of a corenetwork, for example, an ASN-GW.

Referring to FIG. 7, an MS exchanges packets with a CN via a TCPconnection through a BS, an ASN-GW, and an IP network (not shown). Eachtime the MS exchanges a packet via a radio interface in operation 712,the MS resets a timer 704 for idle mode. When the timer 704 for idlemode expires with no further packet exchange, the MS performs aprocedure for entering the idle mode with a paging controller inoperation 714.

Also, each time the CN exchanges a packet with the MS via the TCPconnection in operation 712, the CN starts a timer 702 for TCPKeepAlive. When the timer 702 expires for TCP KeepAlive with no furtherpacket transmission, the CN generates a TCP KeepAlive packet (i.e., aTCP KeepAlive probe packet) directed to the MS in operation 716. The TCPKeepAlive packet is transmitted to the ASN-GW through a P-GW (not shown)over the IP network.

The ASN-GW checks an ACK flag and a data field of the TCP packetreceived from the IP network. If the ACK flag is 1 and the data fieldincludes no data or only 1-byte garbage data, the ASN-GW determines thatthe TCP packet is a TCP KeepAlive packet. Upon receipt of the TCPKeepAlive packet, the ASN-GW determines whether the MS being adestination of the TCP KeepAlive packet is in the idle mode. If the MSis not in the idle mode, the ASN-GW directly transmits the TCP KeepAlivepacket to the MS. On the contrary, if the MS is in the idle mode, theASN-GW directly generates an ACK packet in response to the TCP KeepAlivepacket and transmits the ACK packet to the CN in operation 718. That is,the ASN-GW generates the ACK packet as a response for TCP KeepAlive onbehalf of the MS. While operation 718 is described as taking place afteroperations 720 and 722, operation 718 may be performed at any time afteroperation 716, preferably immediately after operation 716.

While not shown, if the MS does not normally perform an idle-modeoperation such as timer-based location update or the MS performs aderegistration procedure and thus information about the MS is not validany longer, the ASN-GW may generate an RST packet instead of an ACKpacket in response to the TCP KeepAlive packet and reply to the CN withthe RST packet. In this case, the CN terminates (deletes) a TCP sessionfor the MS, upon determining that the TCP session may not be maintainedany longer.

Because a TCP session is an end-to-end connection, the ASN-GW performs apaging procedure for the MS with the paging controller to notify the MSthat the ASN-GW has intercepted the connection between the MS and the CNin operation 720 and transmits a Paging Announce message to a BS(s)neighboring to the MS in operation 722. The Paging Announce messageincludes indication information indicating arrival of the TCP KeepAlivemessage for the TCP session. The indication information may include, forexample, an indication of KeepAlive packet arrival, an IP address of theCN, and a destination TCP port number. In another embodiment of thepresent disclosure, if TCP sessions are mapped to MAC service flows in aone-to-one correspondence and thus a TCP session may be identified justby an ID of a MAC service flow, the indication information may include aService Flow ID (SFID) identifying a service flow associated with theTCP session, if the service flow exists in the MS.

In operation 724, the BS (or the BSs) generates a paging message, thatis, a MOB_PAG-ADV message based on the indication information andbroadcasts the MOB_PAG-ADV message. The MOB_PAG-ADV message includesindication information for TCP KeepAlive along with a parameteridentifying the MS, that is, a MAC address hash value of the MS. Forexample, Action Code of the MOB_PAG-ADV message may be set to 0b11indicating KeepAlive packet, for use as the indication information. Ifthe Action Code of the MOB PAG-ADV message is 0b11, the MOB_PAG-ADVmessage may include additional indication information such as the IPaddress of the CN and the destination TCP port number, to therebyindicate a TCP session for which the TCP KeepAlive packet has beenreceived by the MS.

In operation 726, the MS identifies a TCP session indicated by theindication information included in the MOB_PAG-ADV message and resets atimer for TCP KeepAlive related to the TCP session. Despite reception ofthe MOB_PAG-ADV message, the MS may be kept in the idle mode withoutperforming a paging procedure. This is possible because the MS is awarebased on the indication information that the MOB_PAG-ADV message is notfor paging but for TCP KeepAlive.

Thus, the MS may keep the timer for TCP KeepAlive without unnecessarypaging and network reentry, rather than the MS receiving a pagingmessage, performing network reentry, receiving a TCP KeepAlive packetfrom the network/the BS, and resetting the timer.

If, upon receipt of the MOB PAG-ADV message, the MS determines thatinformation about the TCP session indicated by the indicationinformation included in the MOB_PAG-ADV message has been lost or hasalready been deleted due to a device reset or for any other reason, theMS may operate as follows. In an embodiment of the present disclosure,the MS performs network reentry in response to the MOB_PAG-ADV messageand then transmits an RST packet to the CN. In another embodiment of thepresent disclosure, the MS may request the ASN-GW to transmit an RSTpacket to the CN on behalf of the MS.

In another embodiment of the present disclosure as described below, a BSmay indicate a Location Update (LU) procedure to an MS by a pagingmessage for TCP KeepAlive, rather than the BS including additionalindication information in the paging message.

FIG. 8 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to another embodiment of the presentdisclosure.

Referring to FIG. 8, an MS establishes a TCP connection with a CNthrough a BS, an ASN-GW, and an IP network (not shown) and exchangespackets with the CN via the TCP connection. Each time the MS exchanges apacket via a radio interface in operation 812, the MS resets a timer 804for idle mode. When the timer 804 for idle mode expires with no furtherpacket exchange, the MS performs a procedure for entering the idle modewith a paging controller in operation 814.

Each time the CN exchanges a packet with the MS via the TCP connectionin operation 812, the CN also starts a timer 802 for TCP KeepAlive. Whenthe timer 802 for TCP KeepAlive expires with no further packettransmission, the CN generates a TCP KeepAlive packet (i.e., a TCPKeepAlive probe packet) directed to the MS in operation 816. The TCPKeepAlive packet is transmitted to the ASN-GW through a P-GW (not shown)over the IP network.

Upon receipt of the TCP KeepAlive packet from the IP network, the ASN-GWdetermines whether the MS being a destination of the TCP KeepAlivepacket is in the idle mode. If the MS is in the idle mode, the ASN-GWdirectly generates an ACK packet in response to the TCP KeepAlive packetand transmits the ACK packet to the CN in operation 818. That is, theASN-GW generates the ACK packet as a response for TCP KeepAlive onbehalf of the MS. While operation 818 is described as taking place afteroperations 820 and 822, operation 818 may be performed at any time afteroperation 816, preferably immediately after operation 816.

To notify the MS that the ASN-GW has intercepted the connection betweenthe MS and the CN, the ASN-GW performs a paging procedure for the MSwith the paging controller in operation 820 and transmits a PagingAnnounce message to a BS(s) neighboring to the MS in operation 822. ThePaging Announce message includes indication information indicatingpaging for TCP KeepAlive. The indication information may include, forexample, an indication of KeepAlive packet arrival, an IP address of theCN, and a destination TCP port number. In another embodiment of thepresent disclosure, if TCP sessions are mapped to MAC service flows in aone-to-one correspondence and thus a TCP session may be identified justby an ID of a MAC service flow, the indication information may includean SFID identifying a service flow associated with the TCP session, ifthe service flow exists in the MS.

In operation 824, the BS (or the BSs) generates a paging message, thatis, a MOB_PAG-ADV message based on the indication information andbroadcasts the MOB_PAG-ADV message. The MOB_PAG-ADV message includesindication information for location update along with a parameteridentifying the MS, that is, a MAC address hash value of the MS. Forexample, Action Code of the MOB_PAG-ADV message may be set to 0b01indicating location update, for use as the indication information.

In operation 828, the MS transmits a Ranging Request (RNG-REQ) messageto the BS, requesting location update in response to the location updateindication information included in the MOB_PAG-ADV message. For example,bit 2 of a ranging purpose indication may be set to ‘1’ in the RNG-REQmessage, indicating a location update request.

The MS may reset a timer for TCP KeepAlive in response to theMOB_PAG-ADV message indicating location update in operation 826.

In operation 830, the BS transmits an LU Request (LU-REQ) message to thepaging controller in response to the RNG-REQ message received from theMS. The paging controller updates location information about the MS andthen transmits an LU Response (LU-RSP) message to the BS in operation832. The BS transmits a Ranging Response (RNG-RSP) message to the MS asa response to the location update request of the MS in operation 834.

The RNG-RSP message includes indication information indicating receptionof the TCP KeepAlive packet for the MS from the CN. For example, theindication information includes an indication of KeepAlive packetarrival, an IP address of the CN, and a destination TCP port number. Inanother embodiment of the present disclosure, in the presence of aservice flow related to the TCP session in the MS, the indicationinformation may include an SFID identifying the service flow.

In operation 836, the MS identifies a TCP session indicated by theindication information included in the RNG-RSP message and resets thetimer for TCP KeepAlive in relation to the TCP session.

In another embodiment of the present disclosure as described below, anidle-mode MS transmits a TCP KeepAlive packet (i.e., a TCP KeepAliveprobe packet) to a CN. That is, the MS requests transmission of the TCPKeepAlive packet to an entity of a core network, for example, an ASN-GWby an LU procedure and the ASN-GW transmits the TCP KeepAlive packet tothe CN on behalf of the MS, upon request of the MS.

FIG. 9 is a diagram illustrating a signal flow for a KeepAlive procedureof a network node according to another embodiment of the presentdisclosure.

Referring to FIG. 9, an MS establishes a TCP connection with a CNthrough a BS, an ASN-GW, and an IP network (not shown) and exchangespackets with the CN via the TCP connection in operation 912. Each timethe MS exchanges a packet via a radio interface in operation 912, the MSresets a timer 902 for idle mode. When the timer 902 for idle modeexpires with no further packet exchange, the MS performs a procedure forentering the idle mode with a paging controller in operation 914. Eachtime the MS exchanges a packet via the TCP connection, the MS resets atimer 904 for TCP KeepAlive. When the timer 904 for TCP KeepAliveexpires with no further packet transmission in the idle mode, the MStransmits an RNG-REQ message requesting location update to the BS, forTCP KeepAlive in operation 916. The MS may transmit the RNG-REQ message,maintaining the idle mode. In an embodiment of the present disclosure,bit 2 of a ranging purpose indication may be set to ‘1’ in the RNG-REQmessage, indicating a location update request.

In addition, the RNG-REQ message includes indication information for TCPKeepAlive. For example, the indication information includes requestinformation requesting transmission of a TCP KeepAlive probe or an RSTpacket, an IP address of the CN, and a destination TCP port number. Therequest information refers to a parameter requesting transmission of aTCP KeepAlive probe or an RST packet. In another embodiment of thepresent disclosure, if a service flow related to the TCP session existsin the MS and TCP sessions are mapped to MAC service flows in aone-to-one correspondence, the indication information may furtherinclude an SFID indicating the service flow. For example, if the requestinformation is 0x01, this means a request for transmitting a TCPKeepAlive probe packet on behalf of the MS. If the request informationis 0x02, this means a request for transmitting an RST packet on behalfof the MS.

In operation 918, the BS receives the RNG-REQ message including theindication information and transmits an LU-REQ message including theindication information to the paging controller. The paging controllerforwards the LU-REQ message to the ASN-GW in operation 920. The ASN-GWtransmits a TCP KeepAlive packet to the CN on behalf of the MS inresponse to the request information (0x01) included in the LU-REQmessage in operation 922. The CN resets a timer 906 for TCP KeepAlive inresponse to reception of the TCP KeepAlive packet and then transmits anACK packet as a response for TCP KeepAlive to the ASN-GW in operation924.

In operation 926, the ASN-GW forwards the LU-RSP message in response tothe LU-REQ message to the paging controller. An ACK code indicating thatthe ASN-GW performs TCP KeepAlive on behalf of the MS may be included inthe LU-RSP message.

The paging controller forwards the LU-RSP message to the BS in operation928 and the BS transmits an RNG-RSP message in response to the RNG-REQmessage to the MS in operation 930. The RNG-RSP message may include anACK code indicating a TCP KeepAlive result for the MS. Responseinformation indicating the TCP KeepAlive result is transmitted from theASN-GW to the BS through the paging controller. If the ACK code is setto 0, this indicates successful reception of the response to the TCPKeepAlive packet transmission for the MS. Therefore, the MS resets thetimer for TCP KeepAlive in response to the ACK code in operation 932.

While not shown, if the ASN-GW receives an RST packet in response to theTCP KeepAlive packet transmission, this implies that information aboutthe TCP session is not valid any longer in the CN. Thus, the ACK codethat the ASN-GW transmits to the MS is set to ‘1’ and the MS releases(deletes) the TCP session in response to the ACK code.

If the ASN-GW receives an LU-REQ message including request informationset to 0x02 through the BS, the ASN-GW transmits an RST packet to the CNin response to the request information on behalf of the MS. Then the CNterminates (deletes) the TCP session in response to the RST packet.

FIG. 10 is a block diagram of a network node according to an embodimentof the present disclosure. The network node may be an ASN-GW thatperforms TCP KeepAlive on behalf of an MS.

Referring to FIG. 10, a network interface 1004 receives a TCP packetfrom a CN over a network. A controller 1002 detects that the TCP packetreceived from the network interface 1004 is a TCP KeepAlive packet anddetermines whether an MS being a destination of the TCP packet is in anidle mode based on state information about the MS stored in a memory1006. If the MS is in the idle mode, the controller 1002 transmits anACK packet for TCP KeepAlive to the CN through the network interface1004. The controller 1002 notifies the MS of reception of the TCPKeepAlive packet by a paging procedure.

In another embodiment of the present disclosure, the controller 1002receives an LU-REQ message requesting TCP KeepAlive from an MS throughthe network interface 1004 and transmits a TCP KeepAlive packet to a CNthrough the network interface 1004. Then upon receipt of an ACK packetfor TCP KeepAlive from the CN through the network interface 1004, thecontroller 1002 notifies the MS of reception of the ACK packet by anLU-RSP message.

FIG. 11 is a block diagram of an MS according to an embodiment of thepresent disclosure.

Referring to FIG. 11, a radio interface 1104 receives a paging messageincluding indication information for TCP KeepAlive from a network node,ASN-GW through a BS. The indication information for TCP KeepAlive maythen be stored in a memory 1106. A controller 1102 resets a timer forTCP KeepAlive in response to the indication information of the pagingmessage received from the radio interface 1104. In another embodiment ofthe present disclosure, upon receipt of an LU-RSP message includingindication information for TCP KeepAlive through the radio interface1104, the controller 1102 resets the timer for TCP KeepAlive.

When the timer for TCP KeepAlive expires, the controller 1102 transmitsan LU-REQ message including indication information for TCP KeepAlivethrough the radio interface 1104. Upon receipt of an LU-RSP messageindicating a TCP KeepAlive result through the radio interface 1104, thecontroller 1102 may reset the timer for TCP KeepAlive.

The proposed method and apparatus for performing TCP communication in awireless communication system may be implemented as computer-readablecode in a non-transitory computer-readable recording medium. Thenon-transitory computer-readable recording medium may include any kindof recording device storing computer-readable data. Examples of thenon-transitory computer-readable recording medium may include Read OnlyMemory (ROM), Random Access Memory (RAM), optical disk, magnetic tape,floppy disk, hard disk, non-volatile memory, and the like. In addition,the non-transitory computer-readable recording medium may be distributedover the computer systems connected over the network, andcomputer-readable codes may be stored and executed in a distributedmanner.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure as defined bythe appended claims and their equivalents.

What is claimed is:
 1. A method for performing Transmission ControlProtocol (TCP) communication at a network node in a wirelesscommunication system, the method comprising: receiving, by the networknode that connects between a Mobile Station (MS) and a data network, aTCP KeepAlive packet for maintaining a TCP connection establishedbetween a correspondent node and the MS through the data network fromthe correspondent node; transmitting, by the network node, when it isdetermined that the MS is in an idle mode upon receiving the TCPKeepAlive packet, an acknowledgement packet in response to the TCPKeepAlive packet to the correspondent node; and transmitting, by thenetwork node, indication information indicating the reception of the TCPKeepAlive packet to the MS.
 2. The method of claim 1, wherein theindication information comprises an indication of a TCP KeepAlive packetarrival, an Internet Protocol (IP) address of the correspondent node,and a destination TCP port number.
 3. The method of claim 1, wherein theindication information comprises an indication of a TCP KeepAlive packetarrival and a Service Flow Identifier (SFID) indicating a service flowrelated to the TCP connection.
 4. The method of claim 1, wherein theindication information is transmitted to the MS through a paging requestmessage.
 5. The method of claim 1, wherein the indication information istransmitted to the MS through a location update response message.
 6. Themethod of claim 1, further comprising: transmitting, by the networknode, a paging announce message including the indication information toa Base Station (BS); transmitting, by the BS, a paging message includingan action code indicating a location update request to the MS;transmitting, by the MS, a location update request message to the BS;and transmitting, by the BS, a location update response messageincluding the indication information in response to the location updaterequest message to the MS.
 7. The method of claim 1, further comprisingresetting a timer for TCP KeepAlive related to the TCP connection inresponse to the indication information by the MS.
 8. A method forperforming Transmission Control Protocol (TCP) communication at anetwork node in a wireless communication system, the method comprising:receiving, by the network node that connects between a Mobile Station(MS) and a data network, a location update request message includingindication information for TCP KeepAlive from the MS in an idle mode;transmitting, by the network node, a TCP KeepAlive packet to acorrespondent node that establishes a TCP connection with the MS throughthe data network in response to the indication information; receiving,by the network node, a response to the TCP KeepAlive packet from thecorrespondent node; and transmitting, by the network node, a locationupdate response message including response information indicating aresult of the transmission of the TCP KeepAlive packet to the MS.
 9. Themethod of claim 8, wherein the indication information comprises anindication of a TCP KeepAlive packet arrival, an Internet Protocol (IP)address of the correspondent node, and a destination TCP port number.10. The method of claim 8, wherein the indication information comprisesan indication of a TCP KeepAlive packet arrival and a Service FlowIdentifier (SFID) indicating a service flow related to the TCPconnection.
 11. The method of claim 8, wherein the location updaterequest message further comprises request information requestingtransmission of one of a TCP KeepAlive probe packet and a reset packet.12. The method of claim 8, wherein the response information comprises anacknowledgement code indicating one of successful reception of anacknowledgement packet and reception of a reset packet in response tothe TCP KeepAlive packet.
 13. A method for performing TransmissionControl Protocol (TCP) communication at a Mobile Station (MS) in awireless communication system, the method comprising: transmitting, bythe MS, when a timer for TCP KeepAlive for a TCP connection establishedbetween the MS in an idle mode and a correspondent node through a datanetwork expires, a location update request message including indicationinformation for TCP KeepAlive to a network node that connects betweenthe MS and the data network; receiving, by the MS, a location updateresponse message including response information indicating a TCPKeepAlive result from the network node; and resetting, by the MS, whenthe response information indicates successful reception of anacknowledgement packet for TCP KeepAlive from the correspondent node atthe network node, the timer for TCP KeepAlive.
 14. The method of claim13, wherein the indication information comprises an indication of a TCPKeepAlive packet arrival, an Internet Protocol (IP) address of thecorrespondent node, and a destination TCP port number.
 15. The method ofclaim 13, wherein the indication information comprises an indication ofa TCP KeepAlive packet arrival and a Service Flow Identifier (SFID)indicating a service flow related to the TCP connection.
 16. The methodof claim 13, wherein the location update request message furthercomprises request information requesting transmission of one of a TCPKeepAlive probe packet and a reset packet.
 17. The method of claim 13,wherein the response information comprises an acknowledgement codeindicating one of successful reception of an acknowledgement packet andreception of a reset packet in response to the TCP KeepAlive packet. 18.A network node for controlling a connection between a Mobile Station(MS) and a data network in a wireless communication system, the networknode comprising: a network interface configured to: receive aTransmission Control Protocol (TCP) KeepAlive packet for maintaining aTCP connection established between a correspondent node and the MSthrough the data network from the correspondent node, and transmit anacknowledgement packet in response to the TCP KeepAlive packet to thecorrespondence node; and a controller configured to: control, when it isdetermined that the MS is in an idle mode upon receiving the TCPKeepAlive packet, the network interface to transmit an acknowledgmentpacket in response to the TCP KeepAlive packet to the correspondentnode, and control the network interface to transmit indicationinformation indicating the reception of the TCP KeepAlive packet to theMS.
 19. The network node of claim 18, wherein the indication informationcomprises an indication of a TCP KeepAlive packet arrival, an InternetProtocol (IP) address of the correspondent node, and a destination TCPport number.
 20. The network node of claim 18, wherein the indicationinformation comprises an indication of a TCP KeepAlive packet arrivaland a Service Flow Identifier (SFID) indicating a service flow relatedto the TCP connection.
 21. The network node of claim 18, wherein theindication information is transmitted to the MS through a paging requestmessage.
 22. The network node of claim 18, wherein the indicationinformation is transmitted to the MS through a location update responsemessage.
 23. The network node of claim 18, wherein the network interfaceis further configured to transmit a paging announce message includingthe indication information to a Base Station (BS), wherein the BS isconfigured to transmit a paging message including an action codeindicating a location update request to the MS, wherein the MS isconfigured to transmit a location update request message to the BS, andwherein the BS is further configured to transmit a location updateresponse message including the indication information in response to thelocation update request message to the MS.
 24. The network node of claim18, wherein the MS is configured to reset a timer for TCP KeepAliverelated to the TCP connection in response to the indication information.25. A network node for controlling a connection between a Mobile Station(MS) and a data network in a wireless communication system, the networknode comprising: a network interface configured to: receive a locationupdate request message including indication information for TransmissionControl Protocol (TCP) KeepAlive from the MS in an idle mode, transmit aTCP KeepAlive packet to a correspondent node that establishes a TCPconnection with the MS through the data network in response to theindication information, and receive a response to the TCP KeepAlivepacket from the correspondent node; and a controller configured tocontrol, upon receipt of a response to the TCP KeepAlive packet, thenetwork interface to transmit a location update response messageincluding response information indicating a result of the transmissionof the TCP KeepAlive packet to the MS.
 26. The network node of claim 25,wherein the indication information comprises an indication of a TCPKeepAlive packet arrival, an Internet Protocol (IP) address of thecorrespondent node, and a destination TCP port number.
 27. The networknode of claim 25, wherein the indication information comprises anindication of a TCP KeepAlive packet arrival and a Service FlowIdentifier (SFID) indicating a service flow related to the TCPconnection.
 28. The network node of claim 25, wherein the locationupdate request message further comprises request information requestingtransmission of one of a TCP KeepAlive probe packet and a reset packet.29. The network node of claim 25, wherein the response informationcomprises an acknowledgment code indicating one of successful receptionof an acknowledgment packet and reception of a reset packet in responseto the TCP KeepAlive packet.
 30. A Mobile Station (MS) for performingTransmission Control Protocol (TCP) communication in a wirelesscommunication system, the MS comprising: a controller configured togenerate, when a timer for TCP KeepAlive for a TCP connectionestablished between the MS in an idle mode and a correspondent nodethrough a data network expires, indication information for TCPKeepAlive; and a radio interface configured to: transmit a locationupdate request message including the indication information to a networknode that controls a connection between the MS and the data network, andreceive a location update response message including responseinformation indicating a TCP KeepAlive result from the network node,wherein, when the response information indicates successful reception ofan acknowledgement packet for TCP KeepAlive from the correspondent nodeat the network node, the controller is further configured to reset thetimer for TCP KeepAlive.
 31. The MS of claim 30, wherein the indicationinformation comprises an indication of a TCP KeepAlive packet arrival,an Internet Protocol (IP) address of the correspondent node, and adestination TCP port number.
 32. The MS of claim 30, wherein theindication information comprises an indication of a TCP KeepAlive packetarrival and a Service Flow Identifier (SFID) indicating a service flowrelated to the TCP connection.
 33. The MS of claim 30, wherein thelocation update request message further comprises request informationrequesting transmission of one of a TCP KeepAlive probe packet and areset packet.
 34. The MS of claim 30, wherein the response informationcomprises an acknowledgment code indicating one of successful receptionof an acknowledgment packet and reception of a reset packet in responseto the TCP KeepAlive packet.